In parallel computers connected via a torus or mesh network, the performance of communication among a plurality of nodes (processors) significantly affects the speed of computation processes. As a typical communication pattern, there has been known an all-to-all communication (A2A for short), in which all nodes send data different from each other to other all nodes, requiring the largest amount of communication traffic. The all-to-all communication is known as communication frequently used in a lot of computations including a matrix transpose (T for short) and a fast Fourier transform (FFT for short).
Patent Document 1 defines that a matrix transpose in FFT computation or computation as a two-dimensional (2D) FFT in one-dimensional (1D) FFT computation is the general state of the art. The one-dimensional FFT is processed across a plurality of processors and the two-dimensional FFT is processed across a plurality of processors.
Patent Document 2 describes an idea of making more efficient processing within the all-to-all communication in an n-dimensional torus by superimposing phases. Here, the present invention is described by comparison with Patent Document 2. The present invention is to convert an all-to-all communication to a plurality of partial all-to-all communications to pipeline the all-to-all communications, while the present invention does not include an implementation method within the all-to-all communication and therefore is intended for a different purpose. In addition, scheduled objects of the present invention differ from those of Patent Document 2, and Patent Document 2 does not include the superposition of processes other than those of an all-to-all communication on processes within the all-to-all communication as in the present invention.